In a new class-action suit, plaintiffs say Mallinckrodt broke competition law and dramatically raised prices of H.P. Acthar Gel.

After paying $100 million to settle charges that it quashed competition for its blockbuster H.P. Acthar Gel, Mallinckrodt is facing more legal heat. In a lawsuit (PDF) filed late Monday, plaintiffs representing Medicare Advantage Organizations accuse the company of blocking competition and dramatically raising prices on its lead medication.

The plaintiffs say Mallinckrodt and Questcor have raised H.P. Acthar Gel prices 85,000% since 2001. Mallinckrodt purchased Questcor in 2014 and inherited some of the legal issues tied to the drug, including a Federal Trade Commission probe.

To stifle competition, the plaintiffs argue, Questcor's U.S. unit purchased the rights to a potential competitor from Novartis in 2011, then sidelined that drug and continued raising prices on Acthar. After Mallinckrodt bought Questor, price hikes and anticompetitive behavior continued, the lawsuit claims.

A company spokesperson told FiercePharma, “Mallinckrodt strongly believes that none of the company actions outlined in the plaintiff’s complaint constitute a violation of any law and, therefore, believes that the complaint should be dismissed in its entirety. We will vigorously defend the company in this matter.”

H.P. Acthar Gel, which boasts 19 FDA approvals and generated more than $1 billion last year, now costs the payer-plaintiffs more than $34,000 per vial, according to the lawsuit. In 2001, the price was $40 per vial, the suit claims. The product is an important treatment for infants with epilepsy, and it's also approved to treat a variety of inflammatory conditions.

The company's price increases on Acthar have been smaller than Questcor's were before the buyout, according to recent research, but the drug's growth has been fueled partly by doctors who prescribe the medication frequently. A company spokesperson said the current price per vial for Acthar is $36,382 and that the drugmaker provides discounts to both public and private payers.

The same research found that government programs cover the majority of Acthar scripts. Researchers from Oregon State University’s College of Pharmacy found that the blockbuster drug’s sales have been paid for primarily by Medicare and Medicaid for conditions that often could be treated with less expensive corticosteroids. Spending by Medicare for Acthar increased tenfold and totaled $1.3 billion from 2011 to 2015, the researchers found, in a study published last month in JAMA Internal Medicine.

According to the company's spokesperson, that's a result of practitioners learning more about the drug over time, resulting in "increased usage in aging patient populations, particularly in the rheumatology and pulmonology spaces, where Medicare coverage is more likely to be utilized."

"H.P. Acthar Gel is typically used episodically and acutely with patients, as opposed to a drug that is used regularly or chronically with patients," he said. "Additionally, these patients are often on concurrent treatments."

Mallinckrodt has faced plenty of heat during the yearslong Acthar saga. Earlier this year, it agreed to pay $100 million to the FTC to wrap up a probe it inherited with the Questcor purchase. As part of that deal, the company had to license the competing drug it purchased, Synacthen Depot, for infantile spasms and nephrotic syndrome in the U.S. to West Pharmaceuticals.

According to a New York Post report, it was actually infamous pharma executive Martin Shkreli who blew the whistle on Questcor with a 2014 lawsuit that triggered the FTC investigation. Shkreli now awaits sentencing on securities fraud charges relating to his time at Retrophin.

Since the FTC settlement, Mallinckrodt also left industry trade group PhRMA ahead of new rules requiring members to spend significant money on R&D. The company left the organization only 15 months after joining.

Editor's note: This story was updated with comments from a Mallinckrodt spokesperson.